As crude petroleum rises from the reservoir, it passes through narrow openings, accompanied by water, gases and naturally occurring surfactants. The mixture is agitated as it is pumped up through the production tubing. Such conditions are favorable to the formation of crude petroleum emulsions. Oftentimes, wellbore solids are carried up and flushed out with the crude mixture. The wellbore solids, together with the naturally-occurring surfactants tend to stabilize the emulsions.
These petroleum emulsions cannot be processed further without first removing the major part of the water. The dehydration of petroleum emulsions is generally accomplished by techniques including, but not limited to, settling, heat treatments, centrifuging, by the application of electrical fields or by the addition of demulsifiers. Many petroleum emulsions are usually too stable to be broken solely by the mechanical processes mentioned above within the required time frames. The use of chemical demulsifiers has proven more effective in resolving crude petroleum emulsions. The chemical demulsifiers exert a direct influence on the interfaces of the crude petroleum emulsions and cause a breaking or separation of the petroleum emulsions at lower temperatures and with shorter treatment times than if the demulsifiers are not used.
A large number of patents describe the preparation of chemical demulsifiers. This is largely due to the fact that petroleum emulsions vary in their compositions and characteristics depending on a number of factors including, but not limited to, geographical location and production method. A demulsifier which works well with petroleum emulsions for one location may be ineffective in other locations. It is thus imprecise to say that because a demulsifier does not work well in all applications that it is a poor demulsifier.
For example, U.S. Pat. No. 2,839,489 describes a method of making phenolic polyepoxide modified oxyalkylation derivatives, which are in turn obtained by oxyalkylation of phenol-aldehyde resins. The phenolic polyepoxides used herein always have more than one epoxide group per molecule, and may include a portion of compounds having more than two epoxide groups per molecule. These derivatives are noted as useful as demulsifying agents in preventing, breaking or resolving emulsions of the water-in-oil type, and particularly petroleum emulsions.
Compositions of matter and breaking water-in-oil petroleum emulsions therewith are also subjects of U.S. Pat. No. 3,383,325. The compositions involve a substantially water-insoluble, at least partially oil-soluble product formed by the reaction of (A) a polyoxyalkylene alcohol in which the oxyalkylene groups consist essentially of a member from the group consisting of oxypropylene, oxybutylene and both oxypropylene and oxybutylene with at least one terminal 2-hydroxyethyl group and (B) a diglyddyl ether of a bis-phenol compound in which about 60% to 90% of said diglycidyl ether groups are reacted with the hydroxyl groups of said polyoxyalkylene glycol with the formation of ether linkages between the polyoxyalkylene glycol nuclei and the bis-phenol compound nudei. The remaining, unreacted glycidyl ether groups of the resultant product are reacted with hydroxyl groups on (C) polyoxyalkylene groups of a polyoxyalkylated alkyl phenol-formaldehyde polycondensate with the formation of ether linkages between said reaction product of (A) and (B) and said polyoxyalkylated polycondensate.
U.S. Pat. No. 3,383,326 teaches compositions of matter for breaking petroleum emulsions of the water-in-oil type similar to that of U.S. Pat. No. 3,383,325 discussed immediately above. In the '326 patent, the compositions are the reaction product of an epoxide of a polyphenol and an adduct obtained by reacting ethylene oxide with a higher alkylene oxide adduct of a compound from the group of compounds consisting of hydroxyhydrocarbyl compounds and hydroxyhydrocarbylether compounds, said hydroxyhydrocarbyl compounds and hydroxyhydrocarbylether compounds containing up to 12 carbon atoms and 1 to 3 hydroxyl groups, and the oxyalkylene groups of said higher alkylene oxide adduct being from the group consisting of oxypropylene, oxybutylene and mixtures of oxypropylene and oxybutylene. U.S. Pat. No. 3,676,501 describes products of the reaction of polyoxyalkylene alcohols and diglycidyl ethers of bis-phenol compounds similar to those of the '325 and '326 patents discussed immediately above.
Demulsification processes using polyglycidyl polymers and copolymers thereof and derivatives thereof as demulsifiers are described in U.S. Pat. No. 3,579,466.
As noted, many emulsion breakers are very specific to certain areas and particular crude oil compositions. Most commercial emulsion breakers are formulations or blends of several chemicals. As the production field ages or more wells are put into production, new chemicals or new blends may have to be put into the system. Thus, there is a continuing need for new demulsifiers to address the varying crudes and conditions under which they are produced.